A new extractive spectrophotometric method, which is sensitive, is described for the determination of pentachlorophenol (PCP), a widely used insecticide and herbicide. The method is based on the reaction of pentachlorophenol with concentrated nitric acid at elevated temperature to form chloranil, which liberates iodine with potassium iodide. The liberated iodine then forms yellow brown coloured complex with cetyltrimethyl-ammoniumbromide (CTAB) having absorption maximum at 390 nm and extractable into isoamyl alcohol. Beer’s law is obeyed over the concentration range of 2.5-20 g of PCP in a final solution 100 mL (0.025-0.20 ppm) and has molar absorptivity and Sandell’s sensitivity values of 9.6105 L mol-1 cm-1 and 0.000277-gcm-2, respectively. The detection limit and quantification limit for the proposed method is found to be 0.0018 and 0.0063 ppm, respectively. The method has been satisfactorily applied for the determination of PCP in water, plant material and biological samples.

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